The need for rapid and direct determination of oxidizable solutes in water is evident by comparison to the well known and frequently used indirect biological oxygen demand (BOD) method which ordinarily requires five days and the chemical oxygen demand (COD) method which requires about two hours. These two methods, though widely used, are slow, indirect, and not entirely interchangeable as to results obtained.(1) Another evidence of the importance for such measurements is the total organic carbon method which is based on combustion or high temperature or uv-radiative exhaustive oxidation of organics followed by infra-red absorption determination of the carbon dioxide produced.(1) FNT (1) Standard Methods for the Examination of Water and Wastewater, M. H. Franson (Ed.), Am. Public Health Assoc., Washington, DC, 1989, pp 5-1 to 5-18.
It is an object of this invention to provide an analytical technique and instrument in which pretreatment of a working electrode consisting of a metal that has an oxide surface of that metal on its surface, the timing of both the pretreatment and the monitoring mode, the monitoring of the open circuit potential, and the holding of the final potential for recording are performed in less than two minutes so that direct, rapid, and convenient determinations can be performed with minimal operator training. Although there are numerous reports on the potentiostatic and potentiodynamic responses of nickel oxide electrodes (2), no reports were found on the analytical applications of the potentiometric response of an anodically pre-treated nickel oxide electrode in alkaline electrolyte. Potentiometry offers simplicity in instrumentation and data handling. There are often fewer interferences from mass transport, charging current, and electrolytic reaction processes. FNT (2) Hui, B. and Huber, C. O., Anal. Chim. Acta, 243, (1991) 279-285.